The subject of the invention is a method of making a strip of zircaloy 2 or 4 with good formability.
In the publication by CHARQUET D., ALHERITIERE, E., and BLANC, TG., "Cold-Rolled and Annealed Textures of Zircaloy-4 Thin Strips", Zirconium in the Nuclear Industry: Seventh International Symposium ASTM STP 936 R.B., Adamson and L.F.P. Van Swan, Eds., American Society for Testing of Materials, Philadelphia, 1987, pages 663-672, the authors state that the texture of zircaloy strips has a great effect on their mechanical properties and formability.
The T texture of crystal orientation is similar to that of pure zirconium; in it the base poles (0002) are typically disoriented by 20.degree. to 40.degree. towards the transverse direction, while the [1120] is parallel to the rolling direction. The T texture has a better breaking load, creep strength and deformability (bending or stretch forming) than so-called C textures (centred isotrope) or L textures (base poles swung towards the rolling direction). The effect of cold rolling and annealing on texture is also discussed in this document; a return to a T structure is no longer possible once an L or C structure has been obtained.
An initial T structure is obtained by hot rolling in the alpha range, but the preservation of a T structure through cold rolling and annealing cycles is uncertain.
Applicants have sought to define the conditions which will ensure that the T structure is preserved, so that the formability of the corresponding strips of ZIRCALOY 4 or ZIRCALOY 2 can be improved systematically.
It will be recalled that the composition of these two alloys is given in the ASTM B 352-79 specifications; ZIRCALOY 4 and ZIRCALOY 2 correspond respectively to grades R 60804 and R 60802.